Interface layer for the fabrication of electronic devices

ABSTRACT

The present invention is directed to methods for making electronic devices with a thin anisotropic conducting layer interface layer formed between a substrate and an active device layer that is preferably patterned conductive layer. The interface layer preferably provides Ohmic and/or rectifying contact between the active device layer and the substrate and preferably provides good adhesion of the active device layer to the substrate. The active device layer is preferably fashioned from a nanoparticle ink solution that is patterned using embossing methods or other suitable printing and/or imaging methods. The active device layer is preferably patterned into an array of gate structures suitable for the fabrication of thin film transistors and the like.

FIELD OF THE INVENTION

The present invention relates to electronic devices. More specifically,the present invention relates to the method of fabricating electronicdevices.

BACKGROUND OF THE INVENTION

Ultra-fine particles or nanoparticle (particles having an averagediameter of 200 nanometers or less) are believed to be useful in thefabrication of microelectronic devices. Alivisatos et al., in U.S. Pat.No. 5,262,357, describe a method for making semiconductor nanoparticlesfrom semiconductor precursors. Alivisatos et al. describe using thesesemiconductor nanoparticles to make continuous semiconductor films.Because the semiconductor nanoparticles exhibit significantly lowermelting temperature than bulk materials, a layer of the semiconductornanoparticles can be deposited on a substrate and annealed at relativelylow temperatures, whereby the nanoparticles melt to form a continuousfilm.

One of the goals for nanotechnology is to develop techniques andmaterials that will allow for the fabrication of microelectronic deviceson a variety of substrates using selective deposition, printing and/orimaging technologies. These selective deposition, printing and/orimaging technologies can utilize nanoparticles, or inks comprisingnanoparticles, to fabricate layers in microelectronic devices.

There have been recent efforts to make metal-based solutions, which canbe used to make conductive device layers in the fabrication ofmicroelectronic devices. For example, Kydd in U.S. Pat. No. 5,882,722describes a method of forming conductive layers from a suspension ofmixtures of a metal powder and an organometallic compound dispensed inan organic solvent. The suspension is deposited onto a substrate to forma layer. The layer is then cured to form the conductive layer.

One of the shortcomings of fabricating thin conductive layers withliquids comprising metal-based materials, such as described above, isthat the layers tend to exhibit poor adhesion and delaminate from thesubstrate and/or form irregularities during and/or after the curingprocess. Further, there is a tendency for hillock formation and/or pinhole formation during and/or after the curing process. Therefore, thereis a need to develop suitable substrates and/or methods for depositing,printing and/or imaging liquid metal-based materials, which provideimproved adhesion and reduced topographical irregularities in theresultant films during and/or after the curing process and which can beused to form active device layers in the fabrication of microelectronicdevices.

SUMMARY OF THE INVENTION

The present invention is directed to methods for making electronicdevices, such as thin film transistors (TFTs). In accordance with theembodiments of the invention, an electronic device, or a portionthereof, is fabricated by forming an interface layer on a suitablesubstrate. Preferably, the interface layer is formed from a liquid ink.The interface layer is a continuous interface layer or a patternedinterface layer, as described in detail below. Suitable substratesinclude, but are not limited to, silicon substrates, quartz substrates,glass substrates, metal substrates (such as steel) and polymericsubstrates (such as polyimide). The interface layer is preferably anultra thin layer (on the order or 300 Angstroms or less) and preferablycomprises a metal such as Pd, Pt, Bi, Pb, Sn, Cu, Ni, W, Al, Cr, Mo, Ti,Co, Fe or a combination thereof. The interface layer, in accordance withthe embodiments of the invention, is a metallic layer, a metal oxidelayer, a metal silicide layer or a combination thereof. The interfacelayer, used herein, is not intended to necessarily imply a continuouslayer or a uniform layer. In fact, interface layers, in accordance withthe present invention, can exhibit island structures with regions ofmore and less metal.

In accordance with the preferred method of the invention, an interfacelayer is preferably formed by depositing a liquid ink onto thesubstrate, wherein the interface ink comprises one or more precursorscomprising a metal, such as, Pd, Pt, Bi, Pb, Sn, Cu, Ni, W, Al, Cr, Ti,Co, Fe or Mo and a suitable solvent. The interface precursor ispreferably an organometallic complex including, but not limited to metalcarboxylates, alkoxides, alkyls, aryls, alkynes, alkenes, β-diketonates,amides and thiolates, wherein the solvent is removed and the interfaceprecursor is decomposed to form the interface layer during a thermal,photolytic or e-beam curing process. In yet a further embodiment of theinvention, the interface precursor is a nanoparticle precursorcomprising a metal, such as, Pd, Pt, Bi, Pb, Sn, Cu, Ni, W, Al, Cr, Ti,Co, Fe or Mo. The nanoparticle precursor used for forming interfacelayers preferably comprises nanoparticles that have sizes in a range of1.0-100 nanometers.

On top of the interface layer, an active device layer is formed. Theactive device layer is preferably a conducting layer. The interfacelayer preferably provides ohmic contact between the active device layerand the substrate such as a silicon-wafer or α-Si on glass and helps topromote adhesion of the active device layer to the substrate. Theinterface layer is most preferably an anisotropic conducting layer,wherein the interface layer is conducting through the interface layer tothe substrate, but is semiconducting or insulating laterally along theinterface layer, thereby allowing for the formation of an active devicelayer with electrically isolated regions.

In accordance with the embodiments of the invention, an interface layeris formed by depositing a layer of material that is thicker than 30Angstroms and uniformly etching the layer to a thickness of 30 Angstromsor less. Preferably, the interface layer is deposited to a suitablethickness by spin coating, ink-jet coating, sputter coating or any othersuitable deposition method such as chemical vapor deposition (CVD) orplasma enhanced chemical vapor deposition (PECVD). For example, aninterface layer is formed by depositing a metal precursor, such as anorganometallic precursor, that is thermally and/or photolytically curedand/or decomposed on the substrate to form the interface layer.

In accordance with the embodiments of the invention, an interface layeris formed by depositing the interface precursor on the entire surface ofthe substrate and curing. Alternatively, the interface precursor ispatterned during deposition prior to curing. In yet further embodimentsthe interface layer is patterned at the same time a subsequent devicelayer is patterned. In yet further embodiments of the invention, thepatterned device layer is utilized as a mask for patterning theinterface layer therebelow and/or layers below the interface layer.Preferably, after the interface layer is formed, then the active devicelayer is formed directly on the continuous interface layer or patternedinterface layer to provide the desired electrical contact (Ohmic and/orrectifying) between the active device layer and the substrate.

The active device layer is preferably formed by depositing an inksolution comprising metal nanoparticles. The ink solution preferablycomprises metal nanoparticles comprising one or more metals of Ag, Pd,Rh, Cu, Pt, Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd.Methods for making metal nanoparticles and nanoparticle inks aredescribed in U.S. patent Ser. No. 10/215,952, entitled “NanoparticleSynthesis and the Formation of Inks Therefrom”, the contents of whichare hereby incorporated by reference.

The ink solution is either deposited as a continuous film, which issubsequently patterned, or the ink solution is selectively deposited ina pattern. Methods for coating and patterning ink solutions are furtherdescribed in U.S. patent application Ser. No. 09/525,734, entitled“Fabrication of Finely Features Devices by Liquid Embossing” and in U.S.patent application Ser. No. 09/519,722, entitled “Method forManufacturing Electronic and Electro Mechanical Elements and Device byThin Film Deposition and Imaging”, the contents of which are both herebyincorporated by reference. Regardless of the method of deposition, theink and/or the interface precursor is cured after and/or while beingdeposited onto a suitable substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a-c illustrate a substrate with an interface layer, inaccordance with the embodiments of the invention.

FIG. 2 illustrates depositing a metal nanoparticle ink on a substratewith an interface layer using a micro-pipette technique, in accordancewith the invention.

FIG. 3 illustrates slide coating a continuous film of a metalnanoparticle ink onto a substrate with an interface layer and patterningthe film using an embossing technique, in accordance with the presentinvention.

FIGS. 4 a-d illustrate patterning a continuous layer of metalnanoparticle ink on a substrate with an interface layer and using aliquid embossing technique, in accordance with the invention.

FIGS. 5 a-c illustrate forming a patterned layer of a metal nanoparticleink on a substrate with an interface layer using a micro-stencilingtechnique, in accordance with the invention.

FIG. 6 is a block diagram outlining step for making a device structurecomprising a substrate, an active device layer and an interface layersandwiched between, in accordance with a preferred method of theinvention.

FIGS. 7 a-b are plots of Rutherford Backscattering Data for thinPd-based interface layers, formed in accordance with the embodiments ofthe invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIGS. 1 a-b, in accordance with the embodiments of theinvention, an interface layer 104′ (FIG. 1 b) is formed by depositing athin layer 104 of material comprising a suitable interface precursoronto a substrate 101. The substrate 101 is a silicon, quartz, glass,polymer, metal, or any other substrate suitable for the application athand. The thin layer 104 can be deposited onto the substrate 101 usingany number of methods including, slide bar coating, ink-jet coating,screen printing, dip coating and vapor deposition methods to name a few.Preferably, the thin layer 104 is deposited on the substrate 101 usingspin coating techniques.

In accordance with the embodiments of the invention, the interfaceprecursor comprises of one or more metals of Pd, Pt, Bi, Pb, Sn, Cu, Ni,W, Al, Cr, Ti, Co, Fe or Mo. The interface precursor is preferably anorganometallic complex including, but not limited to metal carboxylates,alkoxides, alkyls, aryls, alkynes, alkenes, β-diktonates, amides andthiolates. In accordance with a preferred method of the invention, themetal precursor comprises a metal carboxylate, such as a metal oleate,2-hexyldecanoate, 2-ethylhexanoate and neodecanoate or combinationthereof, wherein the metal carboxylate is capable of being decomposed onthe substrate 101 by one or more of the curing methods described below.The metal carboxylate, in accordance with the present invention can beformed in situ by mixing a metal complex with a carboxylic acid, alsodescribed below (see examples). In yet a further embodiment of theinvention, the interface precursor are nanoparticles comprising a metal,such as, Pd, Pt, Bi, Pb, Sn, Cu, Ni, W, Al, Cr, Ti, Co, Fe or Mo,wherein the nanoparticles have average sizes in a range of 1.0 to 100nanometers. Nanoparticle precursors can be made to have metal loadingsof 0-50 mass % (based on metal) depending on the solvent(s) and/orsurfactant(s) used.

In accordance with the preferred embodiment of the invention, the thinlayer is formed from a liquid precursor ink comprising the interfaceprecursor and a suitable solvent medium. The interface ink is preferablyformulated by mixing one or more metal complexes of Pd, Bi, Pb, Sn, Cu,W, Ni, Al, Cr, Ti, Co, Fe or Mo in the solvent medium with mass loadingof <5% by Wt. Suitable solvent media include carboxylic acids,hydrocarbons, alcohols, esters, ketones and ethers. Examples include,toluene, cyclohexylbenzene, decaline, 2-ethylhexanol, terpineol,3-octanol 1-octanol, 2-hexyldecanoic acid, 2-ethylhexanoic acid,neodecanoic acid and combinations thereof. Interface ink formulations,in accordance with further embodiments, comprise one or more nonionicsurfactants to help wetting the interface ink onto the substrate 101during the deposition process. Suitable surfactants include, but are notlimited to polyethers, amineoxides, alkyl polyglycosides and fattyalcohols.

In accordance with alternative embodiments of the invention, the liquidprecursor ink comprises metal nanoparticles comprising a metal that isthe same or different than the metal nanoparticles inks used to form theactive device layer.

Still referring to FIGS. 1 a-b, after the layer 104 of interface inkcomprising the interface precursor is deposited onto the substrate 101,then the layer 104 is preferably cured using a radiation source 107 toform a solid interface layer 104′. In the case where the interfaceprecursor is deposited onto the substrate as a liquid precursor ink,curing the layer 104 involves removing the solvent medium anddecomposing the interface precursor. The radiation source 107 isconfigured to deliver heat, light, a beam of electrons 109 or anycombination thereof to the liquid layer 104. Alternatively, or inaddition to using the radiation source 107, a second radiation source111 is used to cure the liquid layer 104, wherein liquid layer 104 iscured through radiation that is transmitted through the substrate 101.

In yet a further embodiment of the invention, after the layer 104 ofinterface ink comprising the interface precursor is deposited onto thesubstrate 101 and the interface precursor is patterned prior to curingusing embossing techniques, such as below. Alternatively, an interfaceink is deposited onto the substrate and device layer ink, for forming anactive device layer, is deposited over the wet interface ink using spincoating for example. In accordance with this embodiment of theinvention, the interface ink layer and the device layer ink arecollectively patterned using embossing techniques, such as describedbelow, and cured after being patterned.

In yet further embodiments of the invention, an interface layer 104′ isformed in situ using chemical vapor deposition techniques, wherein aninterface precursor is cured while being deposited on the substrate 101.For example, an interface precursor, that is either neat or mixed with acarrier gas and/or solvent, is passed over the substrate 101 as achemical vapor in, a vacuum flow chamber (not shown). By controlling theflow of the chemical vapor and the temperature of the substrate, themorphology, the thickness and the composition of the interface layer104′ formed can be controlled. In yet further embodiments of theinvention, deposition of the interface layer from a chemical vaporcomprising the interface precursor is facilitated photolytically or byusing a plasma source.

Regardless of how the interface layer 104′ is formed, the interfacelayer 104′ is preferably a very thin interface layer (on the order of 30Angstroms or less) and is an anisotropic conducting layer, wherein theinterface layer 104′ is conducting in a direction 107 through theinterface layer 104 to the substrate 01, but is semiconducting orinsulating in a direction 109 laterally along the interface layer 104.Accordingly, an active device layer 115 can be formed on the interfacelayer 104′, wherein the active device layer 115 comprises electricallyisolated structures 117. It will be clear to one skilled in the art thatthe interface layer 104′ can be a metallic layer, a metal oxide layer, ametal silicide layer or a combination thereof and the exact compositionof the interface layer 104′ will depend on the precursor, the substrate,the ink formulation and/or the deposition method used.

Referring now to FIG. 1 c, after the interface layer 104′ is formed,then on top of the interface layer 104′ the active device layer 115 isformed. The active device layer 115 is preferably a conductive devicelayer with electrically isolated print features 117, as explainedpreviously, wherein the interface layer 104′ provides ohmic contactbetween the active device layer 115 and the substrate 101 and alsopromotes adhesion of the active device layer 115 to the substrate 101.

Still referring to FIG. 1 c, the active device layer 115 is preferablyformed onto the interface layer 104′ by depositing an ink onto theinterface layer. The ink, in accordance with the embodiments of theinvention is deposited as a continuous film (not shown) which issubsequently patterned with print features 117, or alternatively isselectively deposited as print features 117 using one or more ofdeposition methods described below.

An ink, in accordance with the present invention preferably comprisesmetal nanoparticles comprising one or more metals of Ag, Pd, Rh, Cu, Pt,Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd. Nanoparticles arepreferably formed by reducing a metal precursor in the presence of asuitable reaction medium, such as one or more long branched and/orun-branched carboxylic acids. In a preferred method of the presentinvention, the metal precursor is a metal oxide that is reduced in thereaction medium using a chemical reducing agent, such as an aldehyde, oris thermally reduced by heating a reaction mixture of the precursor andthe reaction medium to temperature sufficient to induce thedecomposition of the metal precursor and/or combination thereof. Thereaction medium, in accordance with the embodiments of the inventionalso comprises solvent and/or surfactants.

After the metal nanoparticles are synthesized, the nanoparticles areisolated, washed and dispersed into a suitable print ink solvent.Alternatively, after the metal nanoparticles are synthesized, the metalnanoparticles are isolated, washed and treated with a suitablesurfactant and then are dispersed into a suitable ink solvent.Additional details of methods for synthesizing metal nanoparticles andinks therefrom are described in U.S. patent Ser. No. 10/215,952, titled“Nanoparticle Synthesis and the Formation of Inks Therefrom”, filed Sep.9, 2002, referenced previously.

A nanoparticle print ink, in accordance with the embodiments of theinvention, is deposited as a continuous film onto the interface layer104′ using ink-jet printing, slide coating, spin coating or any othersuitable deposition method. The continuous film of nanoparticle printink is then patterned using liquid embossing, photo-imaging, etching ora combination thereof. Method for coating and patterning nanoparticleprint inks are further described in U.S. patent application Ser. No.09/525,734, entitled “Fabrication of Finely Features Devices by LiquidEmbossing” and in U.S. patent application Ser. No. 09/519,722, entitled“Method for Manufacturing Electronic and Electro Mechanical Elements andDevice by Thin Film Deposition and Imaging”, also both referencedpreviously.

In yet further embodiments of the invention, a nanoparticle ink isselectively deposited in a pattern of features 117 using one or moreselective deposition techniques, such as ink-jet printing ormicro-stencil printing. Method for selectively depositing nanoparticleinks using Micro-stencil printing techniques are described in U.S.patent application Ser. No. 10/007,122, entitled “Micro-Stencil”, alsoreferenced previously.

When the active device 115 is formed by depositing a liquid nanoparticleink, the printed ink is preferably thermally or photolytically cured tofrom the active device layer 115. In a preferred embodiment of theinvention the active device layer 115 is patterned into an array ofelectrically isolated gate structures suitable for fabrication of thinfilm transistors. FIGS. 2, 3, 4 ac-c and 5 a-c, will now be used toillustrate preferred methods for printing liquid nanoparticle inks ontoan interface layer and active device layer onto a substrate comprisingan interface layer, such as described above.

FIG. 2 illustrates a method of depositing a nanoparticle print ink 206using a micro-pipette 201. In accordance with the embodiments of theinvention, the metal nanoparticle ink 206 is deposited as droplets 203onto a substrate 205 comprising an interface layer 204 to form a imageor pattern of 207 of droplets 203. This, or any other serial deposition,imaging or writing technique, such as ink-jet, can be used to deposit acontinuous or patterned film of nanoparticle ink onto the interfacelayer 204.

FIG. 3 illustrates a system 325 which utilizes a slide coating bar 301with an ink reservoir 305 for depositing a continuous film ofnanoparticle ink onto a flexible substrate 331 with an interface layer(not shown). After the continuous film of nanoparticle print ink isdeposited onto the interface layer of the substrate 331, then the filmis embossed with an embossing drum structure 329 comprising a patternedstamp head 326. The embossing drum structure 329 rolls over thecontinuous film on the substrate 331 to print features 351, 353, 355 and357 onto the film. The system 325 can be configured to move thesubstrate 331 in a direction D1, such that the substrate 331 passesunder a stationary or moving embossing drum structure 329. When themedium 331 is flexible, the system 325 can be configured with rollers360 and 361 for controlling the direction, movement and/or tension ofthe substrate 331.

The system 325 can also be configured with a dryer 303 for curing and/orannealing the printed substrate 331 with photo or thermal energy 309 andan accumulator and/or winder 370 for controlling windup of the printedsubstrate 331. It will be clear to one skilled in the art that thesystem 325 can be equipped with any number of other features including,but not limited to, inspection stations, converting stations andalignment features. Further, the system 300 described above can beconfigured to coat and cure an interface ink in tandem or in a separateprocess.

FIGS. 4 a-e illustrate forming a patterned layer from a continuous layerof nanoparticle ink using a liquid embossing technique. In accordancewith the embodiments of the invention, a substrate 400 is provided withan ultra thin interface layer (30 Angstrom or less) comprising a metaland formed by deposition and decomposition of an interface ink, asdescribed above. After the interface layer 404 is formed, then a thinlayer 405 of nanoparticle print ink is deposited onto the interfacelayer 404, such a shown in FIG. 4 a. The layer 405 can be formed ordeposited onto the interface layer 404 using any suitable techniquesincluding, but not limited to, slide bar coating, ink-jet coating andspin coating.

After the layer 405 of nanoparticle ink is deposited onto the interfacelayer 404, then an elastomeric stamp 410 having a pattern of projectingfeatures 417 and recessed features 420 is lowered until the projectingfeatures 417 make contact with the interface layer 404, therebydisplacing metal nanoparticle ink 405 at the regions of contact, such asshown in FIG. 4 b.

After the layer or metal nanoparticle ink 405 is patterned, then thestamp 410 is removed from the substrate 400 resulting in an array ofprinted features 425 and channels, as shown in FIG. 4 c. The patternedfilm 415 can then be cured, or alternatively cured while the stamp 410is in contact with the substrate 410. In accordance with the preferredmethod of the invention, the channels 430 provide electrical isolationbetween the printed features 425. Further details of stamps and methodsof liquid embossing are described in the U.S. patent application Ser.No. 09/525,734, entitled “Fabrication of Finely Features Devices byLiquid Embossing”, and referenced previously.

Referring to FIG. 4 d, after the patterned film 415 is cured, then thepatterned film 415, in accordance with further embodiments of theinvention, is used as an etch mask to etch the interface layer 404 andfrom a patterned interface layer 404′. In yet further embodiments of theinvention, the patterned film 415 is used as an etch mask to etchinterface layer 404 as well as one or more layers (not shown) below theinterface layer 404.

FIGS. 5 a-c illustrate forming a patterned layer with nanoparticle inkusing micro-stencil techniques. In accordance with the embodiments ofthe invention, a micro-stencil 513 comprises a patterned membrane 504and a nanoparticle ink supply 510. The print ink supply, preferablycomprises a porous structure or membrane, which allows print ink to flowto the print surface 506 of the micro-stencil 513.

To form a patterned layer of nanoparticle ink, an interface layer 503,that is formed on a substrate 501 as described previously, and the printsurface 506 of the micro-stencil 513 are brought together, such that inkis directly transferred onto the interface layer 540 through themembrane 504, as shown in FIG. 5 b.

After the substrate 501 and the print surface 506 are brought together,then the micro-stencil 513 and the substrate 501 are separated leaving apatterned print layer 515 with print features 521, 523 and 525, such asshown in FIG. 5 c. The print layer 515 can then be cured, oralternatively cured while the micro-stencil 513 is in contact with thesubstrate 501. Addition details of micro-stencils and uses thereof aredescribed in U.S. patent application Ser. No. 10/007,122, entitled“Micro-Stencil”, referenced previously.

Regardless of the deposition and/or printing method used, curing metalnanoparticle films typical involves the removal of solvent and/orsurfactant from the printed ink. Cured films can be produced whichexhibit conductivities in a range of 0-100% of that of bulk metal. Curedfilms preferably have thicknesses in a range of about 1.0 nanometers toabout 1000 nanometers and have compositions that correspond to 80% metalor greater.

FIG. 600 is a block diagram outlining steps for making a devicestructure with a substrate, an active device layer and an interfacelayer therebetween, in accordance with a preferred method of theinvention. In the step 601 a layer of an interface ink is deposited ontoa suitable substrate. In accordance with a preferred embodiment of theinvention a Pd-based interface precursor is formed by mixing 0.25 g ofPd(acetate)2, 2.58 g of 2-hexyldecanoic acid in 10 ml of hexane and 10ml of THF for 6 hours at room temperature. The hexane and THF are thenremoved in vacuo to yield a red oil, presumably Pd(2-hexyldecanoate)2.Suitable interface ink formulations are then made by dissolvingPd(2-hexyldecanoate)2 in an appropriate solvent to give inks of Wt. %0-5% Pd. Suitable solvent media include carboxylic acids, hydrocarbons,alcohols, esters, ketones and ethers. Examples include, toluene,cyclohexylbenzene, decaline, 2-ethylhexanol, terpineol, 3-octanol1-octanol, 2-hexyldecanoic acid, 2-ethythexanoic acid, neodecanoic acidand combinations thereof. Interface ink formulations, in accordance withfurther embodiments, comprise one or more nonionic surfactants to helpwetting the interface ink onto the substrate 101 during the depositionprocess. Suitable surfactants include, but are not limited topolyethers, amineoxides, alkyl polyglycosides and fatty alcohols. In yeta further embodiment of the invention a Pd-based interface precursor isformed by mixing 1.0 g of Pd(acetate)2, 2.2.3 g of 2-hexyldecanoic acidand 55 ml of 2-ethylhexanol in a flask for 3 hours at room temperature.The reaction is then filtered to yield a solution of 1% Pd by Wt. in2-ethylhexanol. In this example Pd(2-hexyldecanoate)2 is prepared insitu and used directly without isolation. Similarly, other palladiumcarboxylates may be prepared in this manner and will have the generalformula Pd(OOCR1)(OOCR2) (where R1,2=alkyl, alkenyl, alkynyl or aryl andcontain >5 carbon atoms in length). The length of the carbon chainallows for added stability of the Pd organometallic complex in alcoholsolvents. The Pd ink may then be deposited onto a substrate (typically50 ml are spin coated at 3000 rpm for 30 sec.)

After the interface ink is deposited onto the substrate, such as asilicon substrate, then in step 603, the interface layer is cured at300° C. to yield a thin Pd and/or PdO film and/or PdSi (on the order of30 angstroms or less). The interface ink can be cured using any suitablemethod such as described in detail above.

After the interface layer is cured in step 603, then in step 605nanoparticle ink is deposited onto the cured interface layer, either asa continuous layer that is subsequently patterned or as a patternedlayer. In accordance with a preferred method of the invention thenanoparticle print ink is deposited as a continuous layer and issubsequently embossed, as described above.

In accordance with this preferred method of the invention nanoparticlesare formed from the reduction of a metal oxide. For example, 58 mg Ag2O(0.25 mmol) are dissolved in a mixture of 1.28 g 2-hexyldecanoic acid (5mmol) and 2.27 g 1-dodecene at room temperature and 0.28 g oleic acid (1mmol) is added. The mixture is stirred at room temperature under N2 flowfor about 10 minutes. The reaction mixture is heated up to 150° C. and0.22 ml dodecanal (1 mmol) are injected with a syringe into the reactionmixture. The reaction mixture is stirred at 150° C. under N2 for 90minutes. The reaction is then rapidly cooled down to room temperature.(Reaction volume=5 ml; [Ag]=0.1M; Ag/2=hexyldecanoic acid=1:10; Ag/oleicacid=1:2; Ag/dodccanal=1:2). After the nanoparticle are synthesized,then the nanoparticles are isolated from the reaction mixture. Forexample, 10 ml isopropanol are added to the reaction mixture toprecipitate the Ag nanoparticles. The precipitate is separated from thesupernatant by centrifuging. The precipitate is redissolved in 1 mltoluene. 2 ml isopropanol are then added to this solution. The purifiedAg nanoparticles are obtained as precipitate by centrifuging and thendried for 12 hours under N2 flow. After the nanoparticles are isolated,the nanoparticles are either treated with a surfactant and dissolved inan ink solvent or are directly dissolved in an ink solvent and used toform the layer of nanoparticle ink in the step 605. It is understood,that ink solvent, herein does not necessarily refer to a solvent with asingular molecular composition. In fact, mixtures of solvents are insome cases preferred for formulating ink with properties suitable forthe substrates and/or deposition process used. Further, in accordancewith additional embodiments of the invention, ink formulations includeadhesion and/or hardness promoters. Suitable adhesion and/or hardnesspromoters include metal complexes of Pd, Mg, W, Ni, Cr, Bi, B, Sn, In,Pt. Improved adhesion and hardness has been observed for films printedwith Pd carboxylates (0-10% wt.) added to the ink formulation above.

After the layer of nanoparticle ink is deposited in steps 605, then instep 607, the print is cured to form an active device layer. In theexample above, the resulting active device layer is a patterned silverlayer. As a result of the Pd interface layer formed in steps 603 and605, the patterned silver layer formed in step 607 and 609 showsimproved electrical contact with the substrate, improved adhesion andimproved morphology, in comparison with similar layers formed without aPd-based interfacial layer between the silicon substrate and the patternsilver layer. Further, because the Pd-based interface layer is notconducting laterally, electrically isolated print features can be formedusing the method described above. In accordance with furtherembodiments, in addition to patterning the active device layer, theinterface layer is patterned, such that patterned features of theinterface layer align with patterned features of the active devicelayer. The interface layer is pattered prior to forming the devicelayer, after forming the device layer or while forming the active devicelayer, as described above.

FIGS. 7 a-b are plots of Rutherford Backscattering Data for thinPd-based interface layers formed over a silicon wafer. From the datashown in FIGS. 7 a-b, it is not possible to quantify the actualthickness of the films, but the estimated average thicknesses areroughly on the order of 10-30 Angstrom, corresponding to four to fivemono-layers of palladium atoms.

The present invention has been described in terms of specificembodiments incorporating details to facilitate the understanding of theprinciples of construction and operation of the invention. Examples areprovided for completeness and any number of precursor ink formulationsand print ink formulations are considered to be within the scope of thepresent invention. Such reference herein to specific embodiments anddetails thereof is not intended to limit the scope of the claimsappended hereto. It will be apparent to those skilled in the art thatmodifications may be made in the embodiments chosen for illustrationwithout departing from the spirit and scope of the invention.Specifically, while interface layers of the present invention arepreferably used to improve Ohmic contact, adhesion and morphology of aprinted conductive film, however, the present invention has applicationsfor printing any number of films including dielectric films andsemiconducting films in the fabrication of microelectronic devices.

1. A method of making an electronic device the method comprising: a.forming a metal interface layer onto a substrate; and b. forming anactive device layer over the metal interface layer, wherein the metalinterface layer is in ohmic contact with the active device layer and thesubstrate and wherein the metal interface layer comprises an oxide or asilicide of the metal.
 2. The method of claim 1, wherein the metalinterface layer comprises a metal selected from the group consisting ofPd, Pt, Bi, Pb, Sn, Cu, Ni, W, Al, Cr, Ti, Co, Fe and Mo.
 3. The methodof claim 1, wherein the substrate comprises a material selected from thegroup consisting of silicon quartz, glass, metal and polymer.
 4. Themethod of claim 1, wherein the metal interface layer is laterallyinsulating.
 5. The method of claim 1, wherein the metal interface layerhas an average thickness in a range of 1.0 to 300 Angstroms.
 6. Themethod of claim 1, wherein forming the metal interface layer comprises:a. depositing conductive metal layer with a first thickness; and b.etching the conductive metal layer to a second thickness to form themetal interface layer, wherein the metal interface layer is laterallyinsulating.
 7. The method of claim 1, wherein forming the metalinterface layer comprising depositing a metal-based material using amethod selected from the group consisting of screen coating, dipcoating, spin coating, ink-jet coating, sputter coating, slides coating,extrusion coating meniscus coating, and spray coating.
 8. The method ofclaim 1, wherein the forming the metal interface layer comprises: adepositing a metal precursor layer; and b. curing the metal precursorlayer.
 9. The method of claim 8, wherein the metal precursor layercomprises a metal complex, selected from the group consisting ofcarboxylates, alkoxides, alkyls, aryls, alkynes, alkenes, β-diktonates,amides and thiolates.
 10. The method of claim 8, wherein the curing themetal precursor layer comprises a method selected from the groupconsisting of thermal curing, electron beam curing and photo curing. 11.The method of claim 1, wherein forming at least one of the interfacelayer and the active device layer comprises depositing a layer of inksolution comprising metal nanoparticles.
 12. The method of claim 11,wherein the metal nanoparticles comprise a metal selected from the groupconsisting of Ag, Pd, Rh, Cu, Pt, Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co,Ir, Zn and Cd.
 13. The method of claim 11, wherein the layer of inksolution is deposited as a continuous layer of the ink solution.
 14. Themethod of claim 13, wherein the continuous layer of ink solution isdeposited using a method selected from the group consisting of screencoating, dip coating, spin coating, ink-jet coating, sputter coating,slides coating, extrusion coating meniscus coating, and spray coating.15. The method of claim 13, further comprising patterning the continuouslayer of ink solution using a method selected from the group consistingof liquid embossing, imaging and etching.
 16. The method of claim 11,wherein the layer of ink solution is deposited in a pattern.
 17. Themethod of claim 16, wherein the layer of ink solution is deposited in apattern using a method selected from the group consisting of inkjetprinting or micro-stencil printing.
 18. A method of making a conductivedevice layer comprising: a forming an anisotropic conducting layer on asubstrate; and b. forming the conducting device layer on the anisotropicconducting film, wherein the anisotropic conducting film provides ohmiccontact between the conducting device layer and the substrate.
 19. Themethod of claim 18, wherein the anisotropic conducting layer comprises ametal selected from the group consisting of Pd, Pt, Bi, Pb, Sn, Cu, Ni,W, Al, Cr, Ti, Co, Fe and Mo.
 20. The method of claim 18, wherein thesubstrate comprises a material selected from the group consisting of asilicon substrate, a quartz substrate, a glass substrate, metal and apolymeric substrate.
 21. The method of claim 18, wherein the anisotropicconducting layer has an average thickness of 30 Angstroms or less. 22.The method of claim 21, wherein forming the conducting device layercomprises: a. depositing conductive metal layer with an averagethickness greater than 30 Angstroms; and a. etching the conductive metallayer to have the average thickness of 30 Angstroms or less.
 23. Themethod of claim 18, wherein forming the anisotropic conducting layercomprising depositing metal using a method selected from the groupconsisting of spin coating, ink-jet coating and sputter coating.
 24. Themethod of claim 18, wherein the forming anisotropic conducting filmcomprises: a. depositing a metal precursor layer; and b. curing themetal precursor layer.
 25. The method of claim 24, wherein the curingthe metal precursor layer comprises at least one of thermal curing andphoto curing.
 26. The method of claim 18, wherein forming the conductivedevice layer comprises depositing a layer of ink solution comprisingmetal nanoparticles.
 27. The method of claim 26, wherein the metalnanoparticles comprise a metal selected from the group consisting of Ag,Pd, Rh, Cu, Pt, Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd.28. The method of claim 26, wherein forming the conductive device layercomprises depositing a continuous layer of the ink solution.
 29. Themethod of claim 28, wherein the continuous layer of ink solution isdeposited using a method selected from the group consisting of inkjetprinting, slides coating or spin coating.
 30. The method of claim 28,further comprising patterning the continuous layer of ink solution by amethod selected from the group consisting of liquid embossing, imagingand etching.
 31. The method of claim 26, wherein forming the conductivedevice layer comprises depositing the ink solution in a pattern.
 32. Themethod of claim 31, wherein the depositing the ink solution in a patternuses a deposition method selected from the group consisting of ink-jetprinting and micro-stencil printing.
 33. The method of claim 18, whereinthe anisotropic conducting film comprises an oxide or a silicide of themetal.
 34. The method of claim 1, wherein forming an active device layermetal comprises: a. depositing metal nanoparticles comprise a metalselected from the group consisting of Ag, Pd, Rh, Cu, Pt, Ni, Fe, Ru,Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd; and b. curing the metalnanoparticles.
 35. A method of making a conductive device layercomprising: a. depositing a layer of ink solution comprising metalnanoparticles onto a thin metal-based adhesion layer; and b. curing theink solution, wherein the nanoparticles fuse to form the conductivedevice layer.
 36. The method of claim 35, wherein the metalnanoparticles comprise a metal selected from the group consisting of Ag,Pd, Rh, Cu, Pt, Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd.37. The method of claim 35, wherein the layer of ink solution iscontinuous.
 38. The method of claim 35, further comprising patterningthe layer of ink solution prior to curing the ink solution.
 39. Themethod of claim 35, wherein the layer of ink solution is deposited usinga method selected from the group consisting ink-jet coating, slidescoating or spin coating.
 40. The method of claim 38, wherein patterningthe layer of ink solution comprises a step selected from the groupconsisting of embossing, imaging and etching techniques.
 41. The methodof claim 35, wherein layer of ink solution is selectively deposited in apattern.
 42. The method of claim 41, wherein ink solution is selectivelydeposited in a pattern using a method selected from the group consistingof ink-jet printing and micro-stencil printing.
 43. The method of claim35, wherein the curing comprises exposing the layer of ink to radiation.44. The method of claim 35, wherein thin metal-based adhesion layercomprises a metal selected from the group consisting of Pd, Pt, Bi, Pb,Sn, Cu, Ni, W, Al, Cr, Ti, Co, Fe and Mo.
 45. The method of claim 35,wherein the metal interface film is laterally insulating.
 46. The methodof claim 35, further comprising forming the thin metal-based adhesionlayer, wherein forming the thin metal-based adhesion layer comprisesdepositing a layer of liquid comprising metal nanoparticles and curingthe liquid.
 47. The method of claim 46, wherein the metal nanoparticlescomprise a metal selected from the group consisting of Ag, Pd, Rh, Cu,Pt, Ni, Fe, Ru, Os, Mn, Sn, Cr, Mo, W, Co, Ir, Zn and Cd.
 48. A methodof making a device comprising: a. depositing a layer of liquid interfaceink; b. curing layer of liquid interface ink to from an interface layerwith a thickness of 30 Angstroms or less: c. depositing a layer ofliquid device ink; and d. patterning the layer of liquid device ink toform a patterned device layer, wherein the interface layer is in ohmiccontact with the patterned device layer and is laterally insulating. 49.The method of claim 48, further comprising patterning the interfacelayer ink.
 50. The method of claim 49, wherein the interface layer inkis patterned prior to depositing the layer of liquid device ink.
 51. Themethod of claim 50, wherein patterning the interface layer comprisesembossing the layer of interface ink with an elastomeric stamp.
 52. Themethod of claim 49, wherein the interface layer is patternedconcurrently with the layer of liquid device ink.
 53. The method ofclaim 52, wherein patterning the interface layer and the layer of liquiddevice ink concurrently comprises embossing the layer of interface inkand the layer of liquid device ink with an elastomeric stamp.
 54. Themethod of claim 49, wherein patterning the interface layer comprisesetching the interface layer through the patterned device layer.
 55. Themethod of claim 54, further comprising etching at least one device layerbelow the interface layer.
 56. A method of making an electronic devicethe method comprising: a forming a anisotropic conducting metalinterface layer onto a substrate; and b. forming an active device layerover the anisotropic conducting metal interface layer, wherein theanisotropic conducting metal interface layer is in ohmic contact withthe active device layer and the substrate.